Need help with Battle During Ritual (NPC Stats)

[Chaldfont]

I'm running kind of a "season finale" for a campaign before we switch to Eberron. I want this to be a cool session and maybe someone out there can help me out. I need some NPC stats for Friday night.

Without going into a lot of detail, the PCs have teamed up with their arch nemesis in order to research and perform a ritual to bind and dominate a group of doppelganger assassin/spies that are helping a foreign country take over the world. When the ritual starts, the doppelgangers will be instantly aware that someone is trying to bind them. The ones with access to teleport magic will try to disrupt the ritual. The battle, then, will be the party sorcerer participating in the ritual (and knowing that the villain is going to try to double-cross him at any minute) and the rest of the party trying to keep the doppelgangers away. Once the binding ritual is finished, the doppelgangers won't be a threat. They will be bound to a medallion, so anyone who holds it can command them. Should be a cool fight.

So this is what I need help with. There are three PCs of 12th level. The EL should be 12+ since they will be rested up and prepared. I need stats for:

The Hermit of Ogo (aka Dominus Mortis) -- Sor3/Wiz3/Mystic Theurge8
The Disciple (mysterious follower of the Hermit) -- some combination of cool spell casting classes, character level around 10.
The Sashiin (doppelgangers) -- w/ assorted class levels.
Some Devils -- did I mention that the Sashiin work with a group of devils?

Thanks for the help in advance. I'll try to post details on how the ritual will play out later tonight. Someone might be able to steal ideas from it.

 

[Chaldfont]

Oh yeah, I should mention that the PCs will be aided by a group of hobgoblins and simple undead (zombies and skeletons). These are minions of the Hermit, but I don't expect them to live long enough to help him betray the PCs.

 

[Chaldfont]

Here's the ritual. Sorynn is the PC sorcerer. Dominus Mortis is the villain. Sorynn and the others only know about the first part of the ritual. They don't know that DM is going to try to become a lich.

The Ritual
The ritual requires intense concentration during some of the stages. If any of the participants fails a Concentration check, the ritual fails.

1. The Final Preparation of the Focus: In this stage, Sorynn must put the finishing touches on the medallion. This has the side effect of calling the sashiin. Those with the power to teleport will arrive and try to disrupt the ritual.
2. The Payment of Pain: Each participant in the ritual must give of himself. Each voluntarily suffers 1d4 points of damage to each ability score. Concentration DC ??
3. The Payment of Power: Each participant in the ritual must donate magical energy in the form of spell levels. Each round, on his turn, the participant must sacrifice a prepared spell or spell slot. This sacrifice causes a backlash of energy called the Burn. The Burn causes 1d6 points of damage for each spell level donated. X spell levels must be donated by the participants in order to power the ritual (X should be enough to seriously tax the participants). The Burn may be shunted to another participant during a battle of wills. The attacker must make a caster level check with a bonus equal to his spell casting ability bonus. The DC for the roll is the defender’s Will save + 10. DM knows how to do this, the Disciple and Sorynn must learn through their research. Once a defender suffers an attack, he learns how to retaliate. Damage taken during a round makes the Concentration check harder, as normal. (Concentration DC ??)
4. The Sacrifice of Soul: The soul of an intelligent, spell-casting creature must be sacrificed. The soul is destroyed in the process, so the creature cannot be brought back to life by any means. Dominus Mortis will see who is in the worst shape during the Payment of Power and will shunt his Burn towards the weakest of Sorynn and the Disciple. He wants the strongest to be his second sacrifice in the ritual to come. (Concentration DC??)
5. The Amplification of Energies by the Font: The energies harvested in the last three stages must be further amplified. This is done by opening a portal to the Positive Energy plane called the Font. Anything touching the Font is sucked into the Positive Energy plane. The area within 60 feet of the Font takes on a minor positive-dominant planar trait. The area within 30 feet of the Font takes on the major positive-dominant planar trait. The Font may be moved as a sphere of annihilation. By means of a complex feedback mechanism, the energies are increased to incredible magnitude. (Concentration DC ??)
6. The Infusion of Energies into the Focus: At this point, Dominus Mortis will cast dominate person and boost the spell with the harvested, amplified energies. He and Sorynn will then infuse these energies into the medallion. At this point, the sashiin will be bound to whoever wields it. (Concentration DC ??)

Dominus Mortis will not stop at this point. He will continue the ritual in order to become a lich.

7. Opening the Void: Dominus Mortis will now flip the portal from the Positive Energy plane to the Negative Energy plane. The portal now becomes known as the Void. Anything touching the Void is sucked into the Negative Energy plane. The area within 60 feet of the Void takes on a minor negative-dominant planar trait. The area within 30 feet of the Void takes on the major negative-dominant planar trait. The Void may be moved as a sphere of annihilation. (Concentration DC ??)
8. Embracing the Void: The would-be lich and his prepared phylactery must bathe in the negative energy emanating from the Void. If Dominus Mortis does not have the medallion, he will have to get it. (Concentration DC ??)
9. The Sacrifice of the Second Soul: Another sacrifice of an intelligent spell-casting creature will complete the ritual and close the Void. (Concentration DC ??)